Salmonella species are facultative, intracellular parasites that invade the mucous membrane of the epithelial cells and are transmitted to humans mainly through water, meat, eggs and poultry products. Salmonella infection is the most frequent food-borne gastrointestinal disease transmitted from animals to humans. Typhoid fever still remains endemic in many developing countries and non-typhoidal salmonellosis also is a major food-borne disease worldwide and is estimated to be responsible for the deaths of more than 500 people each year, with costs of $1 billion to $1.5 billion annually in the United States alone (Threlfall 1996; Mead et al. “Food-related illness and death in the United States,” Emerg Infect Dis., 1999,5:607–25.) These figures in India are not fully documented but expected to be much higher. To prevent Salmonella infection, good monitoring and screening programs are required. Detection of Salmonella by conventional bacteriological methods are time consuming and usually requires 5 to days. Therefore, efforts have been made by many workers to reduce time required and to increase the sensitivity of the methods to detect Salmonella (Notermans et al. 1997; Ferretti et al., “Twelve-hour PCR-based method for detection of Salmonella spp. in food,” Appl Environ Microbiol., 2001, 67:977–8; Carli et al., “Detection of salmonellae in chicken feces by a combination of tetrathionate broth enrichment, capillary PCR, and capillary gel electrophoresis,” J Clin Microbiol., 2001, 39:1871–6).
Increased public awareness of the health related and economic impact of food-borne contamination and illness has resulted in greater efforts to develop more sensitive methods of pathogenic detection and identification. Advances in molecular biology technology, particularly the polymerase chain reaction (PCR), have allowed more reliable microbial identification and surveillance. PCR has also become a valuable tool for investigating food-borne outbreaks and identification of etiological agents responsible for the microbial epidemics. PCR techniques have provided increased sensitivity, allowed more rapid processing times and enhanced the detection of bacterial pathogens. In addition to analysis of foods, PCR has also been successfully applied for the detection and identification of pathogenic microorganisms in clinical and environmental samples (Simon 1999; White, 1992).
Enterotoxigenicity has been recognized as one of the distinct pathological attributes of diarrhea inducing bacteria. Salmonella serotypes, which are known for their association with gastroenteritis and diarrhea in humans and animals, have also been shown to produce enterotoxin. The stn gene is located at approximately 89 minutes on the Salmonella lyphimurium chromosome and the presence of an intact stn gene contributes significantly to the overall virulence of Salmonella. The present invention relates to the use of stn gene as a detection marker for Salmonella. 